Project Summary Unstable health insurance coverage (i.e., gaining and/or losing coverage over time) affects millions of individuals in the US. The Affordable Care Act (ACA) has helped 16.4 million of the uninsured gain coverage through the expansion of Medicaid in 31 states (including the District of Columbia as of September 1, 2015) and subsidies through the Health Insurance Exchanges (HIE) and is projected to reduce racial/ethnic disparities in coverage. However, disruptions in coverage may continue to be an important post-ACA issue, as changes in eligibility are expected to continue resulting in churning (i.e., losing and/or gaining coverage over time) between coverage through Medicaid, the HIE and employer-provided health insurance. Despite the abundance of research on the uninsured, little is known about how coverage stability affects access to care, especially in terms of disease management and use of preventive services, and whether important differences exist between racial and ethnic groups. The limited amount of research that does exist on coverage stability have largely been descriptive and have relied on measures that only capture one aspect of coverage stability at a time (e.g., ever lost coverage in the past year). Additionally, few studies have made use of methods that address the influence of unobservable characteristics that may be associated with both coverage stability and access to care (i.e., endogeneity of health insurance coverage). Thus, to address these gaps in the literature, the proposed dissertation will use data on a nationally representative sample of non-elderly adults (ages 18-64) from the Medical Expenditure Panel Survey (MEPS) to: (1) Construct a coverage stability index measure that encompasses multiple aspects of coverage stability using month-to-month coverage status and principal component analysis; (2) Evaluate the effect of coverage stability on disease management among those living with a chronic condition (i.e., diabetes, hypertension, and high cholesterol) by race/ethnicity; and (3) Examine the effect of coverage stability on the use of preventive services among the near-elderly (ages 50-64) by race/ethnicity. The proposed project will contribute and improve upon the existing body of research by developing and testing a coverage stability measure that accounts for multiple aspects of the phenomenon, demonstrating the effect of coverage stability on access to care among vulnerable populations and disparities by race/ethnicity, and making use of methods that address the endogeneity of coverage to produce less biased estimates. Such a contribution would bring to light the magnitude of the issue and provoke urgency among policymakers and other stakeholders to engage in discussions and efforts geared towards identifying those at highest risk for unstable coverage and developing strategies that will make coverage transitions less burdensome on access to care, thus alleviating the perpetuation of racial/ethnic disparities in health.